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Nautic Star 1810 prop size

Hey guys. I'm running an 1810 Nautic Star bay boat with a 115 Yamaha 4 stroke. I cruise at about 35 mph and WOT is approx. 41 mph. I've seen posts on the Nautic Star facebook of others running the same boat (one guy had a Suziki 4 stroke vs. Yamaha) and they claim they achieve WOT of over 50 mph. Although I'm not very concerned about the speed, I'm wondering if I would be able to get better mileage with a different prop. Yamaha performance bulletins only available for this boat with a 90 four stroke. I believe my prop is 13 X 19. Any input is appreciated.
Sometimes , more HP will help on fuel mileage . A smaller motor will strain more to push a heavy boat , therefore burning more gas . The guys that are getting 50 mph may have bigger motors .

The lower pitched props will get you on plane fast but less speed once you get up . Usually a lower pitched prop will make your rpms jump up too high also .

A 115 4 stroke just doesn't seem like enough motor for a 18' bay boat .
The boat is max rated for a 115. They actually come with a
90 hp standard and you have to upgrade to the 115. They guys that said they were getting in the 50's had 115's.
That's crazy . I could be wrong but even if you had the ideal prop , for your boat , I wouldn't think it would give you an extra 15 mph . You need to put the guys that say they running 50 mph on a polygraph .. Lol good luck though !
there are alot of factors that go into boat performance ie.
Are these other guys runnung with a jackplate?
The further back your motor sits affects how its going to perform

is your motor too deep in the water?
Raising your motor helps your lift; however you have to be careful too high and you don't get enough water pressure to keep your motor cool. You should have a water preasure guage before raising your motor.

your prop as well. just like the previous comment the pitch of your prop, how many blades, and if it has been washed out without being worked.

All of these factors affect the performance of any boat
Finfanatic - maybe the other guys are running 2 strokes ? Nothing against 4 strokes because I'll be getting one in the future strictly for gas mileage, but a 2 stroke has a lil bit more get up and go than a 4 stroke , IMO . 15 more mph on the same type boats ? Maybe ...
The gent in question said he did not have a jack plate. I agree that the prop prob. won't get me an extra 15 mph. It may be a bit of a fish story on his part. I'm comfortable with my cruising speed and rarely run WOT, so I'll probably just put this to bed and enjoy the rig the way it is. I'm able to run from the East Pear River Launch on Hwy 90 well into the Biloxi Marsh (I pick my days) on half a tank of gas (35 gallon tank), so I have been prett happy with that performance. It just peaked my curiosity when I saw his claimed top end speed. I've had the boat since March 2010 and have been very pleased with the ride (most of my buds with other brand boats are impressed at how dry mine is)and quality. No, it's not a Yellowfin, Triton, Skeeter, etc., but for what I paid, it's been a good rig. Thanks for the input, guys.
i have 19.6 bay boat w/ a 115 yamaha. i top out at about 41 with good conditions. i have a 17 pitch prop. at 41 i am turning 55 hundred rpms. i tried a 19 pich and could only turn 5000 rpms. i my opinion you are where you should be. 50 mph is a lot to ask out of a heavy bay boat w/ a 115
I'd have to see it to believe it. My Blazer Bay 1860 with the factory 115 Johnson 2 stroke with a 14 3/4 x 21 Viper prop would only turn 44 wide open 5500rpms with a light load. I don't see a 115 turning 50mph especially a 4 stroke. With my 130 2 stroke I'm pushing 48 wide open
Google ' yamaha performance bullentins'
They have what you are looking for.